Electrostatic oiling apparatus



Oct. 17, 1961 E. LOES 3,004,

ELECTROSTATIC OILING APPARATUS Filed April 24, 1959 Power Source 2 Sheets-Sheet a.

ERIK L055 INVENTOR Attorney Oct. 17, 1961 E. LOES ELECTROSTATIC OILING APPARATUS 2 Sheets-Sheet 2 Filed April 24, 1959 IN VE/VTOR E R//( L 05.5 57 W Af/orney M0 for Power pp y 3,004,514 Patented Oct. 17, 1961 3,004,514 ELECTROSTATIC OILING APPARATUS Erik Lees, Pittsburg, Califi, assignor to United States Steel Corporation, a corporation of New Jersey Filed Apr. 24, 1959, Ser. No. 308,754 2 Claims. (Cl. 118-8) This invention relates to improved apparatus for the electrostatic deposition of a thin film of oil or other lubricatingmaterial on continuously moving metallic strip.

It is customary to apply a thin film of lubricant to the surface of tin plate to facilitate the assorting and handling of the product in subsequent can-making operations. The quantity of lubricant which can be applied without interfering in subsequent lacquering or enameling of theplate is extremely small, thus uniformity of film and precise control of deposition are essential. A number of machines utilizing the electrostatic principle of deposition have been devised for this purpose, however the problems of control have not been completely solved. The amount of oil deposited per unit area of a moving strip material is a function of the rate of oil-feed and the lineal speed of strip movement. In prior apparatus, control of oil deposition has been centered about control of oil-feed rate. Efforts in this direction have been at best, only partially successful. The extremely delicate adjustment of oil-feed required has proven impossible to maintain over any practical period of operations, necessitating constant checking and costly recalibration of the apparatus at frequent intervals.

Accordingly, it is an object of the present invention to provide an improved apparatus for applying the thin films of lubricant in rigidly controllable amounts. This and other objects will be made apparent in the following specification when read in conjunction with the attached drawings in which:

FIGURE 1 is a side elevation of the apparatus with the front side removed.

FIGURE 2 is a section taken along the line II--II of FIGURE 1. 7

FIGURE 3 is a sectional view taken along line III-III of FIGURE 1.

FIGURES 4 and 5 are partial views illustrating the effect of the control element of the apparatus at two different conditions of adjustment and,

FIGURE 6 is a schematic diagram showing an arrangement of electrical components for automatically adjusting the position of the control elements in relation to the lineal speed of travel of strip material through the apparatus.

With reference to the drawings, numeral 2 identifies a box-like chamber comprised of sides 3F and 3R, ends 4, a top 5 and a bottom 6 and supported by a framework of structural shapes 7. A metallic strip S to be oiled, enters the chamber through a rectangular conduit 8 disposed centrally of the chamber bottom and comprised of plates 8A and 8B and leaves through a similar conduit 9 centrally disposed in top 5. The chamber shell, its entry and exit conduits are metal, e.g., steel plate, and are electrically grounded through the supporting framework. Welded construction is preferred except for attachment of front side 3F; the latter being made removable to facilitate maintenance and repairs. The strip is maintained in a vertical pass-line by upper and lower conveyor rolls 10 and 11 respectively. At least one of these, e.g., roll 10, is a conventional conductor roll grounded to establish the strip S at ground potential. Attached about mid-height of end walls 4 are a pair of cylindrical, high-voltage insulators 13; each pair supporting a knife-edged discharge electrode 14 of a length slightly greater than that of the widest strip to be processed. Electrodes 14 are disposed in a plane perpendicular to the surface of the strip to extend the width thereof, one to either side of the strip with their knife edges opposed. Attached to the end nearest side 3F of each electrode is a metal rod 15 which extends through a high-voltage insulating bushing 16 carried in front wall 3F. Rods '15 are connected by conductor 17 to one side of a high-voltage D.C. source 18; the other side of which is connected to ground. Suitable controls, not shown,

for disconnecting the source and for varying the potential applied across the electrodes and strip are provided. For the purposes of the invention, source 18 should be capable of supplying up to about 100,000 volts D.C. Associated with each discharge electrode 14 is a controlgrid 19 comprised of a pair of parallelly disposed, spaced apart metal rods or tubes 20 attached at their ends to metal arms 21F and 21R. Arms 21F are rotatably mounted on rods 15 in such manner as to be in good electrical contact therewith and thus establish grid-rods 20 at the same potential as discharge electrode 14. Each arm 21R is carried by a shaft 22 of a non-conductive material. One of the shafts 22 is rotatably mounted in a suitable bearing 23 on side 3R; the other is attached through a suitable coupling to the output shaft of a reversible gear-motor 25. The latter is mounted on the outside of side 3R with its output shaft extending into the chamber through an insulating bushing 26. Each shaft 22 carries a crank-arm 27 and these are coupled together by means of crank-pins 28 and a connecting rod '29 so that the shafts 21 rotate in opposite directions under the control of motor 25. The latter maybe provided with manually operated switches or may be automatically controlled. In either event a pair of conventional, normally closed, cam-operated, limit-switches 30; one in series circuit with; the forward field 25F, the other in series with the reverse field 25R of motor 25, are provided. These switches are set to limit the travel of grids 19 through an arc of about from an upper position, indicated inthe drawings by the grids in solid outline, to a lower position, indicated by the dotted outline thereof. The switches 30 are mounted in a suitable housing 31 and are driven by the motor 25 through belt 32 and sheaves 33. Mounted on top of the chamber 2, one serving each of the electrodes 14, are oil supply tanks 34 which may be interconnected by a conduit 35. Each tank is provided with several oil-feed pipes 36, preferably of a non-conducting material, terminating above the discharge electrodes at spaced intervals along the length thereof. A valve 37 in each line 36 permits regulation of oil delivery by the individual pipes. The oil drips onto the upper surfaces of the electrodes and flows toward the knife-edges thereof. The DC voltage I impressed across the electrodes and strip is sufiicient to ionize air at the electrode edge and the discharge thereof is sufficient to atomize the oil reaching the edge into a mist of substantially negatively charged particles which are immediately attracted toward the positively charged strip. Control of oil deposition as achieved by modifying the paths of travel of these oil particles in a controlled manner. As previously stated, control grids 19 are provided and maintained at the samepotential as the discharge electrodes. In their upper position, indicated by solid lines in the drawings, these grids have little or no effect on the paths of travel of the oil particles and substantially all the oil discharged toward the strip is deposited thereon; this condition is indicated schematically in FIGURE 4. However, as the grids are moved toward their lower position, their strong negative fields become increasingly effective in depressing the paths of travel of the negatively charged oil particles so that an increasing proportion thereof will be deposited on the plates 8A of entry-conduit 8 which, as previously described, are maintained at the same potential as the strip;

3 this condition is illustrated in FIGURE 5. As indicated in the drawings, conduit 8 extends well into the chamber 2so as to facilitate the interception function of its plates 8A and the upper ends of the latter are rolled or otherwise formed inwardly into a drip-lips 38. for conducting intercepted'oil to the-bottom 6. The latter is preferably sloped to form a sump for collection of the excess oil which canthen be removed from time to time and returned .to the tanks 34 by conventional means, not shown. The exact height of intrusion of conduit 8 depends on several factors, including the range of control desired and'is determined during design. While conduit 8 can be fixedly attached to bottom 6, it can conveniently be madeadjustable to facilitate determination of its optimum position by providing a collar 50 attached to the bottom 6 and securing the conduit 8.. therein with setscrews 51.

The described apparatuseliminates the troublesome regulation of .oil-feedvrate as a control measure. That is, it is only necessary to initially adjust valves 37 in the pipes 36 to deliver a uniform supply of oil across the electrodes -14.at a rate suflicient to deposit the heaviest oil film desired at the maximum strip speed contemplated. This is done prior to calibration and with the grids 19 in their uppermost position. Thereafter, any desired proportion of thismaximum oil, as required by the products specification or by changes in the strip speed incident to the processing thereof, can be deposited simplyby regulating the position of control grids 19. The position-of. the grids is visually indicated by pointer 40 and graduated dial 41, the latter attached to the shaft of motor 25' to rotate therewith. The apparatus is calibratedby running strips of different width at various combinations of strip speed and control-grids settings and determining the weight of oil deposited at eachcondition. Operating tables or curves prepared'from the calibration data show the proper dial settings for positioning the grids to deposit a desired weight of oil on a strip of given width and over the strip speed range of the equipment. Any changesin line speed occurring during processing of a-given strip can be compensated by adjusting grid position in accordance with the operating charts. A tachometer generatorA-Z driven by the roll and connected to a suitable voltmeter, not shown, calibrated to read feet, per 'minute provides a visual indicationof the speed of travel of strip through the apparatus. Uncoilers, recoilers .and other conventional units incidental to thehandling of .strip material have not been shown. Such, of course, must be provided if the oiling isconducted as a separate operation. The more common practice however, is to include the oiling apparatus as a unittoward the endofthe tinv coating line. In such multiple-processing installations it is preferable to automatically adjust the position of control grids 19 in response to changes in strip speed. A formof automatic control suitable to this purpose isshown schematically in FIGURE 6. It comprises a potentiometer 43 connected across a suitable reference source of constant DC. voltage and having its contact 43C mechanically coupled to griddrive motor 25 whereby the E.M.F. between one of its ends and its contact is proportional to the position of grids 19. Connected across the tachometer generator 42. is a second-potentiometer 44.providing an proportional to strip speed. A desired proportion of the speed measuring E.'M.F. may be taken ofi through contact 44C. The potentiometers' are polarized and one end of each and the contact thereof are connected to a conventional magnetic amplifier 45 which compares the two E.M.F.s and, if a difference is found, operates control means in the power circuit of the motor 25 to rotate contact 43C in a direction to effect electrical balance of the two signals. Operationo-f motor 25' movescontrol grids 19; thus the grids. arein correct position when the control E.M.-F.s are balanced. The potentiometer 44 is provided with a graduated scale, not shown, and the apparatus calibrated as previously described to provide operating tables giving the initial settingof 44 for various widths of strip and each weight of oil film desired.

While I have shown and described certain specific embodiments of my invention, it will'be apparent that other adaptations and modifications may. be made without departing from the scope of the following claims.

I claim:

1. In apparatus for electrostatically depositing a film of oil on a moving metallic strip including opposed knifeedge discharge, electrodes, means for moving strip therebetween, means for delivering oil to said electrodes, means for imposing an electrical potential across said electrodes and the strip adapted to atomize .the oil'and carry it to the strip, the combination therewith of opposed interceptor plates disposed below said discharge electrodes, opposed adjustable control grids disposed above the discharge electrodes adapted to vary the path of atomized oil-flow downwardly towards said interceptor plates to thereby control the amount ofoil deposited on the strip, and control means adapted, to adjust the position of the control grids automatically in response to changes in speed of travelof the strip.

2. In apparatus for electrostatically depositing a film of oil on a moving metallic strip including opposed knifeedge discharge electrodes extending the width of the strip to be oiled, means for moving strip therebetween, means for delivering oil to said electrodes, means for imposing aD.C. potential'acrossthe electrodes and the strip adapted to atomize the oil and carry it to the strip, the combination therewith of opposed interceptor plates extending the width of the strip disposed'below said discharge electrodes, means for establishing said interceptor plates at the same potential as the strip, opposed adjustably mounted control gridsextending the width-of the strip disposed above said discharge electrodes, means for. establishing said control grids at the same potential as the discharge electrodes, and reversible means adapted to move said control grids toward and away from said interceptor plates to modify the path of atomized oilflowing from the discharge electrodes and thereby control the amount of oil deposited on the strip.

References Cited in the file of this patent 

